Active energy absorbing cellular metals and method of manufacturing and using the same

ABSTRACT

Multifunctional cellular metals (or other materials) for structural applications that are capable of recovering their original (undeformed) shape and thickness after impact or crushing (i.e., self-healing). Alternatively, they may normally be stored or used in their compressed (i.e., crushed) state and deployed when needed to act as energy absorbing structure or packaging (i.e., deployable energy absorber). Additionally, the multifunctional structures may act as an actuator, capable of providing localized or distributed force and displacement, and related methods of using and manufacturing the same. These active cellular metals (or other materials) are composites consisting of conventional metal/alloy truss structures (or other material structures) in combination with shape memory metal/alloy components (or other material components) and offer high specific strength and stiffness, but which are also deployable energy absorbers or self-healing smart structures.

RELATED APPLICATIONS

This application is a national stage filing of International ApplicationNo. PCT/US03/17049, filed on May 30, 2003, which claims benefit under 35U.S.C. Section 119(e) from U.S. Provisional Application Ser. No.60/384,159 filed on May 30, 2002, entitled “Active Energy AbsorbingCellular Metals and Method of Manufacturing the Same,” the entiredisclosures of which are hereby incorporated by reference herein-intheir entirety.

FIELD OF INVENTION

The present invention relates generally to multifunctional cellularmetals for structural applications that are capable of 1) recoveringtheir original (undeformed) shape and thickness after impact or crushing(i.e., self-healing) 2) being stored or used in their compressed (i.e.,crushed) state and deployed when needed to act as energy absorbingstructure or packaging (i.e., deployable energy absorber) and/or 3)acting as an actuator, capable of providing localized or distributedforce and displacement, and related methods of using and manufacturingthe same.

BACKGROUND OF THE INVENTION

Foams and cellular materials are well established as energy absorbingmaterials. Styrofoam packaging for computer monitors during shipping,bubble wrap and cardboard are examples. Their energy absorbingcapability arises from the deformation (bending, stretching, orbuckling) of struts (if open-celled) or membrane walls (if closed-cell)[1]. Closed-cell foams may also rely upon compression of a gas containedwithin the cell to absorb impact energy.

Although the foamed and cellular materials we are most familiar with forpackaging and energy absorption are practically all polymeric, recentdevelopments have led to a variety of metallic counterparts. Metals andalloys are attractive in these applications owing to their much higherstiffness and strength, and the increased energy they can absorb bydeforming plastically (e.g., by dislocation glide). Foamed aluminumalloy can now be produced by injecting air (e.g., Metal Foams: A DesignGuide by Michael Ashby, Anthony Evans, Norman Fleck, Loma Gibson, JohnHutchinson and Haydn Wadley, Butterworths, 2000) or a foaming agent(TiH2) into the liquid melt and solidifying the froth in a steeptemperature gradient at the surface of the bath [2], or by a similar,semi-solid process [3]. These low-cost, high-volume processing routesstrongly encouraged increased research into their performance, and therelation between (porous) structure and performance.

Recent developments by Sypeck and Wadley [4] have led to the developmentand demonstration of low-cost cellular metals based on woven wire trussstructures and formed metal lattices. It is worthwhile to brieflydescribe both of these approaches/materials.

Woven wire truss core sandwich panels use a core consisting of lamina ofwoven wire sheets, which are stacked and bonded using brazing or liquidphase sintering. The lightweight (relative density below 10%) cores arethen bonded to metallic face sheets, which may be of the same or adifferent alloy than the core. Compared to metal foam core panels, suchcellular metal beams and panels have been shown to exhibit excellentspecific stiffness and strength [5]. The formed metal lattice, or simplytruss-core, material is produced by first punching a honeycomb-likearray of hexagonal holes from a flat dense sheet of the desired metal oralloy (e.g. 304 stainless steel); specially-designed tooling (consistingof a pair of interpenetrating arrays of pins) is then used to deform thehex sheet into an array of tetrahedral. This is accomplished by pushingevery second vertex (i.e., node at which three ligaments within the hexsheet come together) upwards, and at the same time, all other verticesin the opposite direction. The resulting truss-core sheets can then bestacked, either with intermediate sheets (or punched hex sheets), andbonded by brazing, sintering, etc.

The cellular metal structures based on woven-wire and truss-coreapproaches are attractive as structural materials because of theirexceptional specific properties. However, they are perhaps even morepromising as candidates for multifunctional materials applications. Inaddition to bearing forces and moments as an integral structuralcomponent, they will simultaneously be used as heat exchangers, filters,catalysts, batteries, energy absorbers, or actuators. Cellular metalsare attractive as energy absorbers not only because they can double asstructural members with high specific stiffness and strength. But alsobecause plastic deformation of metals and alloys is an efficient energyabsorption mechanism, such materials have very low Poisson ratio (theydensify while crushing), and the threshold stress for crushing can beaccurately controlled by the cellular morphology (size, shape of cellsand of the struts and cell walls).

Recent work by Elzey et al. [6] has led to the development of active,shape-morphing structural components based on 2-D and 3-D truss-corestructures combined with SMA elements (actuators). This design has beenshown to provide the capability for fully reversible, shape-changingstructures. Applications might include mission adaptable wings foraircraft, tunable rotors for helicopters and turbine generators, anddeployable space structures. The SMA elements used currently are basedon roughly equi-atomic NiTi, which can be induced to undergo a phasetransformation from its martensite form (monoclinic crystal structure)to austenite (cubic crystal structure) either by increasing thetemperature to above the austenite finish temperature (A_(f)), or byapplying stress at temperatures below the temperature at which theaustenite phase is stable. Deformations of up to 8% strain can beabsorbed at low temperature (e.g.

20) by the formation of the martensite phase, and are completelyrecoverable upon heating to the A_(f) temperature.

The present invention relates to, among other things, low-cost cellularmetals (e.g. truss-core sandwich panel) and active structures to achieveactive, cellular metal materials for use as deployable and reusableenergy absorbers and self-healing structural members. The presentinvention provides low-cost precursors such as the truss-core lattice incombination with active (SMA) elements. The active elements will providefor energy absorption by inelastic deformation (like a conventionalmetal or alloy), but fully recoverable (like a polymer foam).

SUMMARY OF THE INVENTION

The present invention provides multifunctional cellular metals (or othermaterials) for structural applications that are capable of recoveringtheir original (undeformed) shape and thickness after impact or crushing(i.e., self-healing). Alternatively, they may normally be stored or usedin their compressed (i.e., crushed) state and deployed when needed toact as energy absorbing structure or packaging (i.e., deployable energyabsorber). Additionally, present invention multifunctional structuresmay act as an actuator, capable of providing localized or distributedforce and displacement, and related methods of using and manufacturingthe same. These active cellular metals (or other materials) arecomposites consisting of conventional metal/alloy truss structures (orother material structures) in combination with shape memory metal/alloycomponents (or other material components) and offer high specificstrength and stiffness, but which are also deployable energy absorbersor self-healing smart structures.

An aspect of an embodiment of the present invention provides amultifunctional member adapted for structural deformation andreformation. The multifunctional member comprising at least one activecore member. The active core member adapted to deform if exposed to anexternal force and reform from a deformed state if exposed to astimulant. The multifunctional member further comprising at least oneupper member disposed on the core member. The upper member furthercomprises at least one protrusion, whereby the protrusions generallyprotrude in the direction of the active core member. The multifunctionalmember further comprising at least one lower member disposed on the coremember opposite the upper member. The lower member further comprises atleast one protrusion, whereby the protrusions generally protrude in thedirection of the active core member.

At least some of said upper protrusions and lower protrusions arealigned relative to one another such they will interpenetrate whensubject to the force. An aspect of an embodiment of the presentinvention provides a multifunctional member adapted for structuraldeformation and reformation. The multifunctional member comprising atleast one active core member. The active cellular core member adapted todeform if exposed to an external force and reform from a deformed stateif exposed to a stimulant. The multifunctional member further comprisingat least one upper three-dimensional space filling layer disposed on thecore member. The upper three-dimensional space filling layer comprisesan array of out of plane truss units. The multifunctional member furthercomprising at least one lower three-dimensional space filling layerdisposed on the active core member opposite the upper space fillinglayer. The lower three-dimensional space filling layer comprises anarray of out of plane truss units. At least some of the upper and lowerthree-dimensional space filling layers are aligned relative to oneanother such that they will interpenetrate when subjected to the force.

An aspect of an embodiment of the present invention provides amultifunctional member adapted for structural deformation andreformation. The multifunctional member comprising at least one activecore member. The active core member is adapted to deform in tension ifexposed to an external force and reform from a deformed state if exposedto a stimulant. The multifunctional member further comprising at leastone upper expandable layer that is disposed on the core member. Theupper expandable layer comprising an array of expandable units. Theupper expandable units having a base dimension as defined by thedimension substantially parallel to the active core member and a heightdimension as defined by the dimension substantially perpendicular to theactive core member. The multifunctional member further comprising atleast one lower expandable layer disposed on the active core memberopposite the upper space filling layer. The lower expandable layercomprises an array of expandable units. The lower expandable unitshaving a base dimension as defined by the dimension substantiallyparallel to the active core member and a height dimension as defined bythe dimension substantially perpendicular to the active core member. Theupper and lower expandable layers are adapted whereby when subject tothe force the height dimensions of at least some of the upper and lowerexpandable units decrease thereby deforming the active core member intension.

An aspect of an embodiment of the present invention provides amultifunctional member adapted for structural deformation andreformation. The multifunctional member comprising at least one activecore member. The active core member adapted to deform in tension ifexposed to an external force and reform from a deformed state if exposedto a stimulant: The multifunctional member further comprising at leastone upper three-dimensional space filling layer disposed on the coremember. The upper three-dimensional space filling layer comprised of anarray of out of plane truss units. The upper truss units having a basedimension as defined by the dimension substantially parallel to theactive core member and a height dimension as defined by the dimensionsubstantially perpendicular to the active core member. Themultifunctional member further comprising at least one lowerthree-dimensional space filling layer disposed on the active core memberopposite the upper space filling layer. The lower three-dimensionalspace filling layer comprises an array of out of plane truss units. Thelower truss units having a base dimension as defined by the dimensionsubstantially parallel to the active core member and a height dimensionas defined by the dimension substantially perpendicular to the activecore member. The upper and lower three-dimensional space filling layersare adapted whereby when subject to the force the height dimensions ofat least some of the upper and lower truss units decrease therebydeforming the active core member in tension.

An aspect of an embodiment of the present invention provides amultifunctional member adapted for structural deformation andreformation. The multifunctional member comprising at least one activecore member. The active core member adapted to deform if exposed to anexternal force and reform from a deformed state if exposed to astimulant. The multifunctional member further comprising at least oneupper exterior member disposed on the core member and at least one lowerexterior member disposed on the core member opposite the upper exteriormember.

An aspect of an embodiment of the present invention providesmultifunctional member adapted for structural deformation andreformation. The multifunctional member comprising at least one activecore member. The active core member adapted to deform if exposed to anexternal force and reform from a deformed state upon removal of theexternal force. The multifunctional member further comprising at leastone upper member disposed on the core member. The upper member furthercomprises at least one protrusion, whereby the protrusions generallyprotrude in the direction of the active core member. The multifunctionalmember further comprising at least one lower member disposed on the coremember opposite the upper member. The lower member further comprises atleast one protrusion, whereby the protrusions generally protrude in thedirection of the active core member. At least some of the upperprotrusions and lower protrusions are aligned relative to one anothersuch they will interpenetrate when subject to the force.

An aspect of an embodiment of the present invention provides amultifunctional member adapted for structural deformation andreformation. The multifunctional member comprising at least one activecore member. The active cellular core member adapted to deform ifexposed to an external force and reform from a deformed state uponremoval of the external force. The multifunctional member furthercomprising at least one upper three-dimensional space filling layerdisposed on the core member. The upper three-dimensional space fillinglayer comprises an array of out of plane truss units. Themultifunctional member further comprising at least one lowerthree-dimensional space filling layer disposed on the active core memberopposite the upper space filling layer. The lower three-dimensionalspace filling layer comprises an array of out of plane truss units. Atleast some of the upper and lower three-dimensional space filling layersare aligned relative to one another such that they will interpenetratewhen subjected to the force.

An aspect of the present invention provides a multifunctional memberadapted for structural deformation and reformation. The multifunctionalmember comprising at least one active core member. The active coremember adapted to deform in tension if exposed to an external force andreform from a deformed state upon removal of the external force. Themultifunctional member further comprising at least one upper expandablelayer disposed on the core member. The upper expandable layer comprisingan array of out of expandable units. The upper expandable units having abase dimension as defined by the dimension substantially parallel to theactive core member and a height dimension as defined by the dimensionsubstantially perpendicular to the active core member. Themultifunctional member further comprising at least one lower expandablelayer disposed on the active core member opposite the upper spacefilling layer. The lower expandable layer comprises an array ofexpandable units. The lower expandable units having a base dimension asdefined by the dimension substantially parallel to the active coremember and a height dimension as defined by the dimension substantiallyperpendicular to the active core member. The upper and lower expandablelayers are adapted whereby when subject to the force the heightdimensions of at least some of the upper and lower expandable unitsdecrease thereby deforming the active core member in tension.

An aspect of an embodiment of the present invention provides amultifunctional member adapted for structural deformation andreformation. The multifunctional member comprising at least one activecore member. The active core member adapted to deform in tension ifexposed to an external force and reform from a deformed state uponremoval of the external force. The multifunctional member furthercomprising at least one upper three-dimensional space filling layerdisposed on the core member. The upper three-dimensional space fillinglayer comprises an array of out of plane truss units. The upper trussunits having a base dimension as defined by the dimension substantiallyparallel to the active core member and a height dimension as defined bythe dimension substantially perpendicular to the active core member. Themultifunctional member further comprising at least one lowerthree-dimensional space filling layer disposed on the active core memberopposite the upper space filling layer. The lower three-dimensionalspace filling layer comprised of an array of out of plane truss units.The lower truss units having a base dimension as defined by thedimension substantially parallel to the active core member and a heightdimension as defined by the dimension substantially perpendicular to theactive core member. The upper and lower three-dimensional space fillinglayers are adapted whereby when subject to the force the heightdimensions of at least some of the upper and lower truss units decreasethereby deforming the active core member in tension.

An aspect of an embodiment of the present invention provides amultifunctional member adapted for structural deformation andreformation. The multifunctional member comprising at least one activecore member. The active core member adapted to deform if exposed to anexternal force and reform from a deformed state upon removal of theexternal force. The multifunctional member further comprising at leastone upper exterior member disposed on the core member and at least onelower exterior member disposed on the core member opposite the upperexterior member.

An aspect of an embodiment of the present invention provides amultifunctional member adapted for structural deformation andreformation. The multifunctional member comprising at least one activecore member. The active core member adapted to deform if exposed to anexternal force and reform from a deformed state if exposed to astimulant. The multifunctional member further comprising at least oneupper exterior member disposed on the core member and at least one lowerexterior member disposed on the core member opposite the upper exteriormember, wherein at least a portion of at least one upper exterior memberand at least a portion of at least one lower member interpenetrate oneanother when subject to the force.

An aspect of an embodiment of the present invention provides amultifunctional member adapted for structural deformation andreformation. The multifunctional member comprising at least one activecore member. The active core member adapted to deform if exposed to anexternal force and reform from a deformed state upon removal of theexternal force. The multifunctional member further comprising at leastone upper exterior member disposed on the core member at least one lowerexterior member disposed on the core member opposite the upper exteriormember, wherein at least a portion of at least one upper exterior memberand at least a portion of at least one lower member interpenetrate oneanother when subject to the force.

An aspect of an embodiment of the present invention provides amultifunctional member adapted for structural deformation andreformation. The multifunctional member comprising at least one activecore member. The active core member is adapted to deform in tension ifexposed to an external force and reform from a deformed state if exposedto a stimulant. The multifunctional member further comprising at leastone upper expandable layer that is disposed on the core member. Theupper expandable layer comprising an array of expandable units. Theupper expandable units having a base dimension as defined by thedimension substantially parallel to the active core member and a heightdimension as defined by the dimension substantially perpendicular to theactive core member. The multifunctional member further comprising atleast one lower expandable layer disposed on the active core memberopposite the upper space filling layer. The lower expandable layercomprises an array of expandable units. The lower expandable unitshaving a base dimension as defined by the dimension substantiallyparallel to the active core member and a height dimension as defined bythe dimension substantially perpendicular to the active core member. Theupper and lower expandable layers are adapted whereby when subject tothe force the base dimensions of at least some of the upper and lowerexpandable units increase thereby deforming the active core member intension.

An aspect of an embodiment of the present invention provides amultifunctional member adapted for structural deformation andreformation. The multifunctional member comprising at least one activecore member. The active core member adapted to deform in tension ifexposed to an external force and reform from a deformed state if exposedto a stimulant. The multifunctional member further comprising at leastone upper three-dimensional space filling layer disposed on the coremember. The upper three-dimensional space filling layer comprised of anarray of out of plane truss units. The upper truss units having a basedimension as defined by the dimension substantially parallel to theactive core member and a height dimension as defined by the dimensionsubstantially perpendicular to the active core member. Themultifunctional member further comprising at least one lowerthree-dimensional space filling layer disposed on the active core memberopposite the upper space filling layer. The lower three-dimensionalspace filling layer comprises an array of out of plane truss units. Thelower truss units having a base dimension as defined by the dimensionsubstantially parallel to the active core member and a height dimensionas defined by the dimension substantially perpendicular to the activecore member. The upper and lower three-dimensional space filling layersare adapted whereby when subject to the force the base dimensions of atleast some of the upper and lower truss units increase thereby deformingthe active core member in tension.

An aspect of the present invention provides a multifunctional memberadapted for structural deformation and reformation. The multifunctionalmember comprising at least one active core member. The active coremember adapted to deform in tension if exposed to an external force andreform from a deformed state upon removal of the external force. Themultifunctional member further comprising at least one upper expandablelayer disposed on the core member. The upper expandable layer comprisingan array of out of expandable units. The upper expandable units having abase dimension as defined by the dimension substantially parallel to theactive core member and a height dimension as defined by the dimensionsubstantially perpendicular to the active core member. Themultifunctional member further comprising at least one lower expandablelayer disposed on the active core member opposite the upper spacefilling layer. The lower expandable layer comprises an array ofexpandable units. The lower expandable units having a base dimension asdefined by the dimension substantially parallel to the active coremember and a height dimension as defined by the dimension substantiallyperpendicular to the active core member. The upper and lower expandablelayers are adapted whereby when subject to the force the base dimensionsof at least some of the upper and lower expandable units increasethereby deforming the active core member in tension.

An aspect of an embodiment of the present invention provides amultifunctional member adapted for structural deformation andreformation. The multifunctional member comprising at least one activecore member. The active core member adapted to deform in tension ifexposed to an external force and reform from a deformed state uponremoval of the external force. The multifunctional member furthercomprising at least one upper three-dimensional space filling layerdisposed on the core member. The upper three-dimensional space fillinglayer comprises an array of out of plane truss units. The upper trussunits having a base dimension as defined by the dimension substantiallyparallel to the active core member and a height dimension as defined bythe dimension substantially perpendicular to the active core member. Themultifunctional member further comprising at least one lowerthree-dimensional space filling layer disposed on the active core memberopposite the upper space filling layer. The lower three-dimensionalspace filling layer comprised of an array of out of plane truss units.The lower truss units having a base dimension as defined by thedimension substantially parallel to the active core member and a heightdimension as defined by the dimension substantially perpendicular to theactive core member. The upper and lower three-dimensional space fillinglayers are adapted whereby when subject to the force the base dimensionsof at least some of the upper and lower truss units increase therebydeforming the active core member in tension.

These and other objects, along with advantages and features of theinvention disclosed herein, will be made more apparent from thedescription, drawings and claims that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of the presentinvention, as well as the invention itself, will be more fullyunderstood from the following description of preferred embodiments, whenread together with the accompanying drawings, in which:

FIGS. 1(A)-(B) are schematic representations of an embodiment of thepresent invention self-healing/deployable active multifunctional memberin both recovered/deployed configuration and collapsed configuration,respectively.

FIGS. 2(A)-(B) are schematic representations of an embodiment of thepresent invention self-healing/deployable active multifunctional memberin the reformed/deployed configuration and collapsed configuration,respectively, wherein the core is three dimensional.

FIG. 2(C) schematically illustrates an enlarged partial view of aportion of the multifunctional member as shown in FIG. 2(A) wherein theactive core member is aligned above the lower exterior member (the upperexterior member is not shown).

FIGS. 3(A)-(B) are schematic representations of an embodiment of thepresent invention of a scissors type self-healing/deployable activecellular multifunctional member in both reformed/deployed configurationand collapsed configuration, respectively.

FIG. 4(A) schematically illustrates a partial view of an embodiment ofthe present invention scissor type self-healing/deployable activemultifunctional member in the reformed/deployed configuration whereinthe core is three-dimensional.

FIG. 4(B) schematically illustrates a square cell SMA active core memberthat corresponds to pyramidal rigid upper and lower truss members.

FIG. 5 schematically illustrates a partial view of an embodiment of thepresent invention scissor type self-healing/deployable activemultifunctional member in the reformed/deployed configuration whereinthe core is a cellular hex sheet corresponding to tetrahedral rigidupper and lower truss members.

FIG. 6 is a schematic illustration of an active cellular metal appliedas a deployable energy absorber.

FIG. 7 is a schematic illustration of an active cellular metal appliedas a self-healing active cellular metal, wherein the active cellularmetal commences in a deployed state.

FIG. 8 is a schematic representation of an embodiment of the presentinvention self-healing/deployable active multifunctional member in arecovered/deployed configuration having multiple layers.

FIG. 9 is a schematic representation of an embodiment of the presentinvention scissor type self-healing/deployable active multifunctionalmember in a recovered/deployed configuration having multiple layers.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides self-healing or deployable cellularmetals or combination thereof, as well as related methods of using andmanufacturing the same. The present invention provides compositestructures of conventional and shape memory metals or alloys. Thepresent invention relates generally to multifunctional cellular metals(or other materials) for structural applications that are capable of 1)recovering their original (undeformed) shape and thickness after impactor crushing (i.e., self-healing) 2) being stored or used in theircompressed (i.e., crushed) state and deployed when needed to act asenergy absorbing structure or packaging (i.e., deployable energyabsorber) and/or 3) acting as an actuator, capable of providinglocalized or distributed force and displacement, and related methods ofusing and manufacturing the same.

Firstly, in an embodiment the present invention provides a cellulararchitecture/mechanism based on conventional (i.e., non-SMA) metal/alloytruss structures suspended on shape memory alloy elements (wires,strips, ribbons, sheets (continuous or perforated), or the like). Infact, any pair of interpenetrating topology structures when suspended inthis way that responds to compression (crushing or impact) byinterpenetration of the rigid truss structures or protrusions (struts)and consequent deformation of the SMA elements (i.e., suspensionelements) in tension may be utilized.

Secondly, in an embodiment the present invention provides a cellulararchitecture/mechanism analogous to the scissors-jack; it includes rigid(i.e. conventional metal/alloy) truss layers alternating with SMA layersand responds to compression loading by lateral spreading of the trussesor expandable layer, and consequent deformation of the SMA elements intension. Both embodiment types, described in greater detail below,recover their original (undeformed) configuration (size, shape, etc.)upon heating or stimulating of the SMA elements (i.e., self-healing).Alternatively, the SMA elements may be a pseudo-elastic (superelastic)shape memory alloy (SMA) which does not require heat or other stimuli torecover. Rather, the pseudo-elastic (super elastic) shape memory alloy(SMA) returns to a recovered/reformed state spontaneously andimmediately on removal of the external or desired force, i.e., theapplied load.

Alternatively, both of the aforementioned structures may be normallyused in their compressed configuration and expanded by heating otherstimuli (i.e., deployable) prior to use as an impact energy absorber.Such stimuli include, but not limited thereto electric field, magneticfield, and pressure (e.g., pyrotechnic devices). Alternatively, both ofthe aforementioned structures may be a pseudo-elastic (superelastic)shape memory alloy (SMA) which does not require heat or other stimuli torecover. Rather, both of the aforementioned structures may be normallyused in their compressed configuration and expanded spontaneously andimmediately on removal of the external or desired force, i.e., theapplied load.

FIG. 1 schematically illustrates the concept for a two-dimensionalsuspended truss prototype of a multifunctional member 102. FIG. 1(A)schematically illustrates the multifunctional member 102 in a reformedor recovered state, before an external force 104 is applied to themultifunctional member 102. Whereas FIG. 1(B) schematically illustratesthe multifunctional member 102 in a collapsed state, after encounteringan external force 104. Through the addition of heat 106 or otherstimuli, the multifunctional member 102 returns to a recovered/reformedstate as seen in FIG. 1(A). Alternatively, the multifunctional member102 is a pseudo-elastic (superelastic) shape memory alloy (SMA) whichdoes not require heat or other stimuli to recover. Rather, themultifunctional member 102 returns to a recovered/reformed statespontaneously and immediately on removal of the external force 104,i.e., the applied load.

Still referring to FIG. 1(A), exemplary component parts of themultifunctional member 102 are seen. In the center of the member 102 isthe active core member 110, having an upper surface 112, and an opposinglower surface 114. In the present exemplary embodiment, the active coremember 110 is composed of a shape memory alloy (SMA) metallic substance.In proximity to the active core member 110, adjacent its upper surface112, lays a rigid or substantially rigid upper member 116. Next,adjacent the lower surface 114 of the core member 110 lays a rigid orsubstantially rigid lower member 118. The rigid or substantially rigidupper member 116 in the present exemplary embodiment includes amultitude of protrusions 120 or struts or the like adjacent the activecore member upper surface 112. Rigid upper member protrusions 120 orstruts can either be an integral part of rigid upper member 116 orattached thereto. The rigid upper member 116 is connected to active coremember 110 where the multiple protrusions 120 are adjacent the uppersurface 112 of active core member 110 in the present exemplaryembodiment, as shown by reference number 117. The protrusions or strutsas discussed throughout this document maybe a variety of structures suchas projections, fingers, posts, pillars, pedestals, legs, rods, knobs,arms, tongues, embossments, protuberances, cones, frustrums, or thelike. The protrusions may be a variety of sizes and shapes orcombination thereof including, but not limited thereto, the following:triangular, oval, semi-oval, rectangular, convex, cubicle, egg crateshape, spherical, semi-spherical, rectangular, pyramidal, tetrahedral,circular, cup or triangular. It is also contemplated that truss unitsmay be utilized for the protrusions. In fact, any pair ofinterpenetrating topology structures when suspended in this way thatresponds to compression (crushing or impact) by interpenetration of therigid truss structures or protrusions (struts) and consequentdeformation of the SMA elements (i.e., suspension elements) in tensionmay be utilized.

In the present exemplary embodiment, the rigid lower exterior member 118also includes a multitude of protrusions 122 or struts, which can eitherbe an integral part of rigid or substantially rigid lower member 118 orattached thereto. The rigid lower member protrusions 122 are adjacentthe lower surface 114 of the active core member 110. In the presentexemplary embodiment, the rigid lower exterior member 118 is connectedto active core member 110 where the rigid lower member protrusions 122are adjacent the lower surface 114 of active core member 110, as shownby reference number 119.

The upper fastening means 117 and lower fastening means 119 can be avariety of mechanical fasteners, interlocking designs, various bondingmeans, attachment means, or adhesive means. For example, the rigid uppermember 116 and rigid lower member 118 can be attached to the active coremember 110 using, but not limited the following: fusion bond, splicing,crimping, interlocking designs or sockets, adhesives,metallurgical/chemical bonding, and mechanical fasteners (rivets,screws, threaded fasteners, bolts/nuts, etc.), or any other device. Itshould be noted that not all rigid upper member protrusions 120 orstruts and rigid lower member protrusions 122 or struts need be fastenedto active core member 110, such that a select number of attachments canbe made as desired.

Turning to FIG. 1(B), the multifunctional member 102 is seen in thecollapsed state, after being subjected to an external force 104 (shownin FIG. 1(A)). In the present exemplary embodiment, upper protrusions120 are adapted to avoid lower protrusions 122 when the multifunctionalmember 102 is subjected to the external force 104, allowing greaterenergy absorption by the multifunctional member 102. In the presentexemplary embodiment, the rigid upper member 116 and rigid lower member118 do not deform, but instead transfer absorbed energy from theexternal force 104 to the active core member 110. The active core member110 thus deforms in tension when the multifunctional member 102 issubjected to external force 104.

When the active core member 110 of the multifunctional member 102 asseen in collapsed form in FIG. 1(B) is subjected to heat 106 or otherstimuli, it returns to its original, reformed/recovered form as seen inFIG. 1(A). In the present exemplary embodiment, when the SMA active coremember 110 absorbs heat 106 or other stimulants generated by heat sourceor stimulant source (not shown), it reforms to its originalnon-tensioned shape, forcing the entire multifunctional member 102 toreturn to its original undeformed configuration as seen in FIG. 1(A).Alternatively, the SMA active core member 110 is a pseudo-elastic(superelastic) shape memory alloy (SMA) which does not require heat orother stimuli to recover. Rather, the active core member 110 returns toa recovered/reformed state spontaneously and immediately on removal ofthe external force 104, i.e., the applied load.

These approaches are based on a composite structure combining rigidmembers (compression members) with energy absorbing members (tensilemembers). The compression members (rigid upper member 116 and rigidlower member 118) are effectively suspended by the tensile active coremember 110. The underlying concept on which this class of recoverablestructural designs is based is therefore referred to as the suspensionstructure concept. As the rigid upper exterior member 116 and rigidlower exterior member 118 are pressed together, as during an impact forexample, the multifunctional member 102 structure deforms by stretchingthe active core member 110 in tension. The active core member 110 may beshape memory alloy (SMA) wire, strip, ribbon, or sheet (continuous orperforated), or some other suitable, high-strain, recoverable material.This material could be an elastomer, or a shape memory material thatresponds to temperature or magnetic or electric field stimulation.

The multifunctional material 102 may be used as a single layer (i.e. onecomposite unit layer of conventional plus SMA components), or as alaminate of multiple (repeating) unit layers, as shown in FIG. 8, forexample. FIG. 8 schematically illustrates the concept for atwo-dimensional suspended truss prototype of a multifunctional member102 having a multiple repeating layers of the upper exterior members116, rigid lower exterior members 118, and active core members 110.Additional unit layers increases the total energy which can be absorbedon impact and the total deformation which can be recovered onself-healing of the active core member 110.

The multifunctional member 102 of FIG. 1 comprises two opposing sets ofrigid exterior members 116 and 118 (e.g., metal/alloy), each having amultitude of protrusions 120 and 122 (posts, struts or egg crate cups)which are offset such that when adjacent layers of the multifunctionalmember 102 are pressed together, the rigid exterior member protrusions120 and 122 interpenetrate. The rigid exterior member protrusions 120and 122 are interconnected in the present exemplary embodiment by ashape memory alloy (SMA) wire (ribbon or sheet) active core member 110.An external compressive force 104 is applied normal or oblique to theplane of the multifunctional member 102 (as during impact or crushing)that causes the opposing sets of rigid exterior member protrusions 120and 122 to interpenetrate and in doing so, deforms the active coremember 110 in tension. The deformations of the active core member 110material (e.g. SMA) acts to absorb energy during impact/crushing.

Alternatively, as well be discussed in greater detail infra themultifunctional member 102 can be uniformly and intentionally compacted(crushed) into its collapsed state as seen in FIG. 1(B), and deployed byintroducing heat 106 or other stimuli (or alternatively, upon theremoval of a desired, expected, predetermined, resultant, controlledforce or forces) to the SMA active core member 110 just prior to animpact of an external force 104.

The SMA material discussed throughout this document may be made of froma material or composite of materials including, but not limited thereto,the following: Ni—Ti, Ni—Ti—V, Ni—Ti—Fe, Ni—Ti—Cu, Ni—Ti—C—, Ni—Ti—Cr,Ni—Ti—Nb, Ni—Ti—Pd, Ni—Ti—Fe, Cu—Zn—Al, Cu—Al—Ni and Fe—Mn—Si. The SMAmaterial may also include magnetic SMA and polymer SMA.

The upper member 116 and lower member 118 may be comprised of but notlimited to polymers, metals, or ceramics, or any combination thereof.

While FIG. 1 illustrates an exemplary two-dimensional embodiment, thesuspension concept is readily extendable to 3-D architectures, as shownby the exemplary embodiment shown in FIGS. 2(A)-(C). The presentexemplary embodiment uses an upper and a lower layer of truss-corelattice layer 350, 352 comprised of out of plane truss units 354, 356(consisting of tetrahedral or pyramidal elements, for example, as wellas kagome, cone, frustrum, and combinations thereof and othernon-limiting arrangements) as the rigid or substantially rigid uppermember 116 and rigid lower exterior member 118, respectively,alternating with perforated hexagonal cell SMA sheet active core member110. The rigid upper exterior member 116 and rigid lower exterior member118 are stacked directly over one another so that they willinterpenetrate when a crushing force (not shown) is applied normal tothe plane of the multifunctional member 102 as seen in FIG. 2(B). As therigid upper exterior member 116 and the rigid lower exterior member 118layers interpenetrate, the ligaments of the SMA hex cell active coremember 110 are deformed in tension. In the present exemplary embodiment,upon the addition of heat 106 or other stimuli to active core member110, either by direct resistance, or by some other indirect method, toabove the austenite finish A_(f) temperature, the SMA active core member110 will revert to its original undeformed configuration as seen in FIG.2(A). This cycle of deformation by exposing the multifunctional member102 to an external force 104 (not shown), followed by shape memoryrecovery of the active core member 110 that can be repeatedindefinitely.

Alternatively, the active core member 110 is a pseudo-elastic(superelastic) shape memory alloy (SMA) which does not require heat orother stimuli to recover. Rather, the active core member 110 returns toa recovered/reformed state spontaneously and immediately on removal ofthe external force 104 (not shown), i.e., the applied load.

As for the SMA material discussed throughout this document, the SMA'scould be those that are stimulated by temperature or magnetic or otherstimuli. As an example, consider the metal SMA systems. These should beheated to ensure that they are in the austenite condition, and theheating will be to a temperature to above the so called austenite finishA_(f). That's the characteristic temperature to insure that the entireshape memory alloy has reverted to the austenite phase, i.e. the hightemperature phase, i.e., the transition temperature. Typically, this isapproximately in the range of about 0 to about 170° C., but may be asbroad as about −20 to about 770° C. Other transformation temperatureranges may be affected by selecting the alloy composition as required bythe intended application, e.g., an optimal temperature range can bechosen by selecting the appropriate actuator material.

Moreover, the various embodiments described herein, the active cores areprovided with a means of heating to a temperature sufficient to achievethe temperature range at the level or rate of change deemed adequate forthe intended application. Heating or stimulation may be achieved bydirect resistance (Joule) heating of the SMA face sheet (i.e. by theattachment of suitable electrical contacts and the passage of currentthrough the face sheet), by resistance heating of a conductor attachedto, or located within the active core, by the use of a heated fluid orgas, by radiative means (e.g. Xenon lamp, laser, etc.), or otheralternative approaches as appreciated by those skilled in the art. Otherstimulation may eventually include electric, magnetic, electromagnetic,or perhaps sound fields.

Alternatively, as will be discussed in greater detail infra themultifunctional member 102 can be uniformly and intentionally compacted(crushed) into its collapsed state as seen in FIG. 2B, and deployed byintroducing heat (not shown) or other stimuli (or alternatively, uponthe removal of a desired, expected, predetermined, resultant, orcontrolled force or forces) to the SMA active core member 110 just priorto an impact of an external force 104.

Referring to FIG. 2(A), layers of tetrahedral truss core material formedof metal/alloy or polymer rigid members 116 and 118 alternate with alayer of perforated SMA sheet active core member 110 there between. Thetetrahedral layers are positioned such that the rigid (or substantiallyrigid) upper member 116 and rigid (or substantially rigid) lowerexterior members 118 nest (interpenetrate) when exposed to an externalforce (not shown) during compression or crushing as seen in FIG. 2(B).As for the 2-D case, the SMA active core member 110 is deformed intension as the rigid upper member 116 and rigid lower member 118 layersare pressed together (i.e., towards one another) by the external force.To recover the reformed/undeformed configuration of the multifunctionalmember 102, the SMA active core member 110 in the present exemplaryembodiment is heated (or stimulated) to above the austenite finish A_(f)temperature or stimulated state as required.

Alternatively, the active core member 110 is a pseudo-elastic(superelastic) shape memory alloy (SMA) which does not require heat orother stimuli to recover. Rather, the active core member 110 returns toa recovered/reformed state spontaneously and immediately on removal ofthe external force 104 (not shown), i.e., the applied load.

Turning to FIG. 2(C), FIG. 2(C) schematically illustrates an enlargedpartial view of a portion of the multifunctional member 102 with thelower member 118 aligned with perforated hexagonal cell SMA sheet activecore member 110. Reference number 121 reveals the location where thenode or leg of the upper exterior member 116 (not shown in this view)would contact the upper surface of the active core member 112.

An embodiment of the present invention multifunction member is ascissors jack-like concept as illustrated in FIGS. 3(A)-(B). Thescissors jack design concept again relies on truss structuresconstructed using metal/alloy or polymers and which are subjectedprimarily to compression and SMA elements deforming in tension and whichexhibits deployable/self-healing active behavior. Generally speaking, inits classic configuration, this device comprises four rigid strutsconnected by pivot points or pins at their ends to form a trapezoid (orbetter, a diamond shape). If two opposite pivot points or pins arepulled towards one another, the remaining adjacent or proximate twopivot points or pins are forced outwards, away from one another. Forexample, the automobile scissors jack relies on a threaded bolt or screwto pull the pivot points or pins together, thereby lifting a car as theother two pins are forced apart. Conversely, as the car presses down onthe jack, it applies a tensile force to the screw.

The present invention cellular metal energy absorbing multifunctionalmember concept replaces the screw actuator with a shape memory alloyelement (wire, strip, ribbon, band, sheet (continuous or perforated), orthe like) active core member 210 and upper expandable layer 240 andlower expandable layer 242 (e.g., rigid links) comprised of rigid orsubstantially rigid upper expandable units 244 and lower expandableunits 246.

FIG. 3(A) shows an example of a 2-D prototype of the scissors-typestructure; the present exemplary embodiment comprises two layers ofcorrugated metal sheet (e.g., 304 stainless steel), to form the upperexpandable layer 240 and a lower expandable layer 242 arranged in mirrorsymmetry or substantially mirror symmetry about a central SMA activecore member 210 sheet. The reformed/undeformed repeating scissors jackelement is readily visible when viewed on end, as in FIG. 3(A). As themultifunctional member 202 is compressed when exposed to an externalforce 204 during impact, the corrugated rigid upper and lower expandablelayers 240 and 242 (which experience compressive loading) transmittensile load to the SMA active core member 210, deforming it in tensionin lateral directions or near lateral directions. The resultingstructure can be viewed in FIG. 3(B). The multifunctional member 202absorbs energy as it crushes and may be recovered/reformed (redeployed)by applying heat 206 or other stimuli from a heat source (not shown) tothe SMA active core member 210 in quantity to bring it to its austenitefinish A_(f) temperature or stimulated state. Alternatively, themultifunctional member 202 is a pseudo-elastic (superelastic) shapememory alloy (SMA) which does not require heat or other stimuli torecover. Rather, the multifunctional member 202 returns to arecovered/reformed state spontaneously and immediately on removal of theexternal force 204, i.e., the applied load.

In the present exemplary embodiment, upper expandable units 224 eachhave two dimensions. The first of upper expandable units 244 dimensionis b_(u), the linear (or substantially linear) distance measured fromone point of contact of the upper expandable unit 244 with the uppersurface 212 of active core member 210 to the next immediate such pointof contact. The dimension b_(u) is at least substantially parallel tothe upper surface 212 of active core member 210. The second of upperexpandable units 246 dimension is h_(u), the linear distance measured atleast substantially perpendicularly from the upper surface 212 of activecore member 210 to a point on the upper expandable unit 244 furthestfrom the upper surface 212 of the active core member 210.

Similarly, in the present exemplary embodiment, lower expandable unit246 has two dimensions. The first of lower expandable unit dimensions isb_(l), the linear distance measured from one point of contact of thelower expandable unit 246 with the lower surface 214 of active coremember 210 to the next immediate such point of contact. The dimensionb_(l) is parallel to the lower surface 214 of active core member 210.The second of lower expandable unit 246 dimension is h_(l), the lineardistance measured at least substantially perpendicularly from the lowersurface 214 of active core member 210 to a point on the lower expandableunit 246 furthest from the lower surface 214 of the active core member210.

In the present exemplary embodiment, when the multifunctional member 202seen in FIG. 3(A) is exposed to an external force 204, the dimensionsb_(u) and b_(l) increase, while the dimensions h_(u) and h_(l) decrease.Conversely, when the SMA active core member 210 of the multifunctionalmember 202 seen in FIG. 3(B) is exposed to heat 206 and reforms to itsoriginal undeformed/reformed configuration, the dimensions b_(u) andb_(l) decrease, while the dimensions h_(u) and h_(l) increase.Alternatively, the multifunctional member 202 is a pseudo-elastic(superelastic) shape memory alloy (SMA) which does not require heat orother stimuli to recover. Rather, the multifunctional member 202 returnsto a recovered/reformed state spontaneously and immediately on removalof the external force 204, i.e., the applied load, and reforms to itsoriginal undeformed/reformed configuration, the dimensions b_(u) andb_(l) decrease, while the dimensions h_(u) and h_(l) increase.

The multifunctional structure 202 may be used as a single layer (i.e.one composite unit layer of conventional plus SMA components), or as alaminate of multiple (repeating) unit layers, as shown in FIG. 9, forexample. FIG. 9 schematically illustrates the concept for atwo-dimensional scissor truss prototype of a multifunctional member 202having a multiple repeating layers of the upper exterior members 216,rigid lower exterior members 218, upper expandable layer 240, lowerexpandable layer 242 and active core members 210. Additional unit layersincreases the total energy which can be absorbed on impact and the totaldeformation which can be recovered on self-healing of the active coremember 210.

Turning to FIGS. 4(A)-(B), FIGS. 4(A)-(B) schematically illustratepartial view of an embodiment of the present invention scissor typeself-healing/deployable active multifunctional member 302 in thereformed/deployed configuration wherein the core is three dimensional.As illustrated, for the suspended structure concept, the scissorsstructure may be extended to 3-D architectures. This example comprisesupper three-dimensional space filling layer 350 comprising pyramidalrigid upper truss units 354 and lower three-dimensional space fillinglayer 352 comprising lower truss units 356 that sandwich perforatedsquare cell SMA active core member 310 sheets. While FIGS. 4(A)-(B) onlyshow a limited number of pyramidal rigid upper truss units 324 and lowertruss units 356 for the sake of simplifying the drawings, it should beunderstood that a predetermined number of truss units 354, 356 may beutilized with the multifunction member 302.

Looking particularly at FIGS. 4(A)-(B), in contrast with the suspendedstructure of FIG. 2, the pyramid units in the present exemplaryembodiment are now positioned in mirror symmetry about the SMA sheet310. Thus, rather than interpenetrating during crushing when themultifunctional member 302 is exposed to an external force (not shown),the pyramids are forced to spread laterally or substantially lateral(i.e. in the plane of the sheet the dimensions b_(u) and b_(l)increasing), stretching the SMA ligaments of the active core member 310as they do so. The desired upper three-dimensional space filling layer350 comprised of upper out of plane truss units 354 and the lowerthree-dimensional space filing layer 352 comprised of lower out of planetruss units 356 are spread laterally.

In some embodiments, the scissors-type structures comprise pin,rotation, pivot joints/attachments 319 or suitable means to accommodaterelative rotation of compressive struts during crushing.

In operation, when the multifunctional member 302 seen in FIGS. 4(A)-(B)is exposed to an external force 304, the dimensions b_(u) and b_(l)increase, while the dimensions h_(u) and h_(l) decrease. Next, when theSMA active core member 310 of the multifunctional member 302 is exposedto heat (not shown) and reforms to its original undeformed/reformedconfiguration, the dimensions b_(u) and b_(l) decrease, while thedimensions h_(u) and h_(l) increase. Alternatively, the multifunctionalmember 302 is a pseudo-elastic (superelastic) shape memory alloy (SMA)which does not require heat or other stimuli to recover. Rather, themultifunctional member 302 returns to a recovered/reformed statespontaneously and immediately on removal of the external force, i.e.,the applied load, and reforms to its original undeformed/reformedconfiguration, the dimensions b_(u) and b_(l) decrease, while thedimensions h_(u) and h_(l) increase.

Similarly, turning to FIG. 5, FIG. 5 schematically illustrates a partialview of an embodiment of the present invention scissor typeself-healing/deployable active multifunctional member 302 in thereformed/deployed configuration wherein the active core 310 is hexagonalcellular. As illustrated, for the suspended structure concept, thescissors structure may be extended to 3-D architectures. This examplecomprises an upper three-dimensional space filling layer 350 comprisedof tetrahedral truss units 354 and lower three-dimensional space fillinglayer 352 comprised of tetrahedral truss units 356 that sandwichperforated hex cell SMA active core member sheets 310. While FIG. 5 onlyshow a limited number of upper tetrahedral truss units 354 and lowertetrahedral truss units 356 for the sake of simplifying the drawings, itshould be understood that a predetermined number of truss units may beutilized with the multifunction member 302.

Looking particularly at FIG. 5, in contrast with the suspended structureof FIG. 2, the tetrahedra in the present exemplary embodiment are nowpositioned in mirror symmetry about the SMA sheet 310. Thus, rather thaninterpenetrating during crushing when the multifunctional member 302 isexposed to an external force (not shown), the tetrahedra are forced tospread laterally or substantially lateral (i.e. in the plane of thesheet the dimensions b_(u and b) _(l) are increasing), stretching theSMA ligaments or legs of the active core member 310 as they do so.

The active cellular metal based on the scissors-type design provides astrong tendency to expand laterally or near laterally during crushing.If crushing is localized, as during indentation, material surroundingthe indentation must somehow accommodate the lateral deformation. Insome applications, it shall be important to avoid local buckling ofcompressive struts, which will occur if no accommodation mechanism isavailable. Further, scissors-type structures incur relative rotation ofcompressive struts during crushing. In the absence of any mechanism forrotation of the struts (e.g. pin joint or pivot joints, journals), therotation must occur by localized deformations in the region where two ormore struts connect with each other. Clearly, unless these deformationsare kept acceptably small, struts will fail at or near the joint due tostatic overload or fatigue.

Turning to FIGS. 6(A)-(C), FIG. 6(A) schematically illustrate how any ofthe herein mentioned active cores of the multifunctional members can beapplied as a deployable energy absorber. The multifunctional member 495has a active core member 480 that is shown first in its normal(compressed) configuration with the upper exterior member 470 and lowerexterior member 490 (FIG. 6(A). Next; heating of the SMA elements to theA_(f) temperature or stimulating the SMA elements causes the cellularstructure to deploy as shown in FIG. 6(B). Alternatively, themultifunctional member 495 is a pseudo-elastic (superelastic) shapememory alloy (SMA) which does not require heat or other stimuli torecover. Rather, the multifunctional member 495 returns to arecovered/reformed state spontaneously and immediately on removal of adesired force, i.e., the applied load. The material is then able toabsorb energy during an impact by (tensile) deformation of the SMAsubstructure as shown in FIG. 6(C). Finally, the material can becompressed to its normal configuration, ready to be re-deployed ondemand as shown in FIG. 6(D).

In contrast, FIG. 7(A) schematically illustrates the multifunctionalmember already in its deployed sate, i.e., the original (undeformed)configuration. As such, as shown in FIG. 7(B), the multifunctionalmember 495 is subjected to deformation as a result of impact. Finally,the material is able to recover (self heal) its original configurationby activating the shape memory element as shown in FIG. 7(C).Alternatively, the multifunctional member 495 is a pseudo-elastic(superelastic) shape memory alloy (SMA) which does not require heat orother stimuli for activation to recover. Rather, the multifunctionalmember 495 returns to a recovered/reformed state spontaneously andimmediately on removal of a desired force, i.e., the applied load.

Regarding the manufacturing and process development, the active cellularmetals described herein may be based on composite laminates ofconventional metal/alloy and shape memory alloy precursors, joined(metallurgically or by some other means) to create the final material.The conventional metal/alloy precursors may be manufactured from sheetstock formed either by deformation processing alone (e.g. corrugatedsheet structure) or produced by a combination of cutting/punching andforming operations (i.e. the tetrahedral truss-core material). The SMAprecursor (or other active material) is either wire, strip or sheet(either as-received or perforated to create a hexagonal cell array).

Conventional metal/alloy and SMA components may be joinedmetallurgically at moderate temperature by soldering (e.g. using aspecially developed flux in combination with Ag—Sn solder [7]).Intermediate and high temperature joining processes may include brazingand liquid phase sintering. More costly alternatives such as laser andelectron beam welding have also demonstrated successful joining withonly a moderate effect on shape memory performance reported [8]. Thus,in summary, available bonding techniques include, but not limited to thefollowing: brazing bonded, UV welding bonded, laser welding bonded,electron beam welded, resistance welded, ultrasonically/friction welded,fusion welded or diffusion welding bonded.

Design and manufacture is also affected by the method chosen for heatingthe SMA during deployment/healing. Direct resistance (Joule) heating maybe considered, but since the SMA components will not, in general, beisolated from contact with the metallic compression components, this maybe inefficient and, perhaps more importantly, slow. Alternative meanswould include use of insulated resistance heating elements (e.g.polyamide coated NiCr wire) either bonded to or wrapped around SMAelements, or the flow of a heated fluid through the cellular structure.

According to the design criteria discussed throughout, SMA attributesand structures may be implemented with the present invention asdescribed in the co-pending and commonly assigned PCT Application No.:U.S. 02/27116 filed Aug. 26, 2002, entitled “Reversible Shape MemoryMultifunctional Structural Designs and Method of Using the Same,”(Publication No.: WO 03/018853 A2) and corresponding U.S. applicationSer. No. 10/487,291, filed Feb. 20, 2004, of which are incorporated byreference herein in their entirety.

According to the design criteria discussed throughout, othertwo-dimensional and three-dimensional structures may be implemented withthe present invention as shown in co-pending and co-assigned PCTInternational Application No. PCT/US02/17942, entitled “MultifunctionalPeriodic Cellular Solids And The Method Of Making Thereof,” filed onJun. 6, 2002, and corresponding U.S. patent application Ser. No.10/479,833, filed Dec. 5, 2004, of which are hereby incorporated byreference herein in their entirety.

According to the design criteria discussed throughout, othertwo-dimensional and three-dimensional structures may be implemented withthe present invention as provided in co-pending and co-assigned PCTInternational Application No. PCT/US01/17363, entitled “MultifunctionalPeriodic Cellular Solids and the Method of Making thereof,” filed on May29, 2001, and corresponding U.S. application Ser. No. 10/296,728, filedNov. 25, 2002, of which are hereby incorporated by reference herein intheir entirety.

According to the design criteria discussed throughout, othertwo-dimensional and three-dimensional structures may be implemented withthe present invention as shown in co-pending and co-assigned PCTInternational Application No. PCT/US03/16844, entitled “Method forManufacture of Periodic Cellular Structure and Resulting PeriodicCellular Structure,” filed on May 29, 2003, and corresponding U.S.application Ser. No. ______, filed Nov. 23, 2004, of which are herebyincorporated by reference herein in their entirety.

The publications as cited throughout this document and provided beloware hereby incorporated by reference herein in their entirety.

-   [1] Gibson, L. and Ashby, M. F., Cellular Solids—Structure and    Properties, Pergamon Press (1988).-   [2] Miyoshi, T., Itoh, M., Akiyama, S. and Kitahara, A., “Aluminum    Foam ALPORAS: Production process, properties and applications”,    MRS V. 521, 133 (1998).-   [3] Banhart, J. and Baumeister, J., “Production methods for Metallic    Foams”, MRS V. 521, 133 (1998).-   [4] Sypeck, D. S. and Wadley, H. N. G., “Cellular Metal Truss core    Sandwich Structures”, MetFoam 2001 Conf. Proc. (2001).-   [5] Mumm, D. R., Chiras, S., Evans, A. G., Hutchinson, J. W.,    Sypeck, D. J. and Wadley, H. N. G., “On the Performance of    Lightweight Metallic Panels Fabricated Using Textile Technology”,    submitted (2001).-   [6] Elzey, D. M., Sofia, A. and Wadley, H. N. G., “Shape    memory-based multifunctional actuator panels”, In: Industrial and    Commercial Applications of Smart Structures and Technologies,    Proceedings of SPIE Vol. 4698 (2002).-   [7] Pelton, A., Nitinol Devices and Components, NDC NT Flux,    Fremont, Calif.-   [8] Tuissi, A., Besseghini, S., Squatrito, F., Pozzi, M., “Effect of    Nd-YAG laser welding on the functional properties of Ni-49.6 at. %    Ti”, Mat. Sci. & Eng. A 273-275, pp. 813-817 (1999).

In conclusion, some advantages of the present invention multifunctionalcellular structures is that it they are capable of 1) recovering theiroriginal (undeformed) shape and thickness after impact or crushing(i.e., self-healing), 2) being stored or used in their compressed (i.e.,crushed) state and deployed when needed to act as energy absorbingstructure or packaging (i.e., deployable energy absorber), and/or 3)acting as an actuator, capable of providing localized or distributedforce and displacement.

Other advantages of the present invention multifunctional cellularstructures, and related methods of using and manufacturing the same, arethat they provide: lightweight structural material which is deployableon demand to absorb impact energy; capability to store structurescompactly when not in use (undeployed) to absorb energy; light, stiff,and strong structural characteristics; corrosion resistant material ifdesired; low cost manufacturing capability; and high specific energyabsorption with design-tunable crushing stress.

Further advantages of the present invention multifunctional cellularstructures (especially panels), and related methods of using andmanufacturing the same, are that they provide: lightweight structuralintegrity; moderately strong, stiff load-bearing materials; andcapability of being joined by conventional joining and attachment means(brazing, welding, mechanical fasteners, etc).

Still yet, advantages of the present invention multifunctional cellularstructures (especially panels), and related methods of using andmanufacturing the same, are that they may be applied to a variety ofapplications including, but not limited thereto: crash/impact energyabsorption (deployable) systems for automobile interiors, packaging,crates, containers, weapons containers tossed/parachuted fromaircraft/helicopters, architectural applications, interior/exteriorpanels/padding, aircraft interiors, and military vehicle interiors.

Finally, advantages of the present invention multifunctional cellularstructures (especially panels), and related methods of using andmanufacturing the same, are that they may be applied to a variety ofapplications including, but not limited thereto self-healing cellularmetals, automatic body panels, boats/ships hull cladding, and train carsinterior/exterior.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. Of course, itshould be understood that a wide range of changes and modifications canbe made to the preferred embodiment described above. The foregoingembodiments are therefore to be considered in all respects illustrativerather than limiting of the invention described herein. Scope of theinvention is thus indicated by the appended claims as read in light ofthe foregoing description, including all equivalents, and all changeswhich come within the meaning and range of equivalency of the claims aretherefore intended to be embraced herein.

1. A multifunctional member adapted for structural deformation andreformation, the multifunctional member comprising: at least one activecore member, said active core member adapted to: deform if exposed to anexternal force, and reform from a deformed state if exposed to astimulant; at least one upper member disposed on said core member, saidupper member further comprised of at least one protrusion, whereby saidprotrusions generally protruding in the direction of said active coremember; at least one lower member disposed on said core member oppositesaid upper member, said lower member further comprised of at least oneprotrusion, whereby said protrusions generally protruding in thedirection of said active core member; and said at least some of saidupper protrusions and lower protrusions are aligned relative to oneanother such they will interpenetrate when subject to the force.
 2. Themultifunctional member of claim 1, wherein said stimulant is heat. 3.The multifunctional member of claim 1, wherein stimulant provides atleast one transition temperature range to said active core member. 4.The multifunctional member of claim 3, wherein said transitiontemperature range is between about −20° C. to about 770° C.
 5. Themultifunctional member of claim 3, wherein said transition temperaturerange is between about 20° C. to about 120° C.
 6. The multifunctionalmember of claim 3, wherein said transition temperature ranges are about50° C. to about 70° C.
 7. The multifunctional member of claim 1, whereinsaid stimulant is at least one of electric field, electromagnetic field,and magnetic field, or any combination thereof.
 8. The multifunctionalmember of claim 7, wherein said active core member is repeatedly exposedto deformation and said stimulant, said active core member is adapted toperform fully reversible cyclic shape changes between deformed andreformed states.
 9. The multifunctional member of claim 1, wherein saidactive core member is operable to alter the shape of the multifunctionalmember.
 10. The multifunctional member of claim 1, wherein said activecore is made from a material selected from the group consisting ofNi—Ti, Ni—Ti—V, Ni—Ti—Fe, Ni—Ti—Cu, Ni—Ti—C—, Ni—Ti—Cr, Ni—Ti—Nb,Ni—Ti—Pd, Ni—Ti—Fe, Cu—Zn—Al, Cu—Al—Ni and Fe—Mn—Si.
 11. Themultifunctional member of claim 1, wherein said core is made fromcomposites formed of one or more of a material selected from the groupconsisting of Ni—Ti, Ni—Ti—V, Ni—Ti—Fe, Ni—Ti—Cu, Ni—Ti—C—, Ni—Ti—Cr,Ni—Ti—Nb, Ni—Ti—Pd, Ni—Ti—Fe, Cu—Zn—Al, Cu—Al—Ni and Fe—Mn—Si.
 12. Themultifunctional member of claim 1, wherein said active core is made fromat least one of an elastomer material, a magnetic SMA material, and apolymer SMA material or any combination thereof.
 13. The multifunctionalmember of claim 1, wherein at least some of said protrusions of saidupper member and said lower member are comprised of at least one shapeor combination of the shapes including oval, semi-oval, triangular,rectangular, convex, cubicle, egg crate cup shape, spherical,semi-spherical, rectangular, pyramidal, tetrahedral, circular, frustrum,conical, or triangular.
 14. The multifunctional member of claim 1,wherein said active core is bonded to at least some of said protrusions,wherein said bond is at least one of brazing bonded, UV welding bonded,laser welding bonded, electron beam welded, resistance welded,ultrasonically/friction welded, fusion welded or diffusion weldingbonded.
 15. The multifunctional member of claim 1, wherein said activecore is attached to at least some of said protrusions, wherein saidattachment is at least one of splicing, crimping, interlocking designsor sockets, adhesives, metallurgical/chemical and mechanical fasteners.16. The multifunctional member of claim 15, wherein said mechanicalfasteners include at least one of rivets, screws, threaded fasteners,and bolts and nuts.
 17. The multifunctional member of claim 1, whereinsaid upper member and said lower member are made from a materialselected from the group consisting of polymers, metals, and ceramics.18. The multifunctional member of claim 1, wherein said upper member andlower member are made from composites formed of one or more of amaterial selected from the group consisting of polymers, metals, andceramics.
 19. A multifunctional member adapted for structuraldeformation and reformation, the multifunctional member comprising: atleast one active core member, said active cellular core member adaptedto: deform if exposed to an external force, and reform from a deformedstate if exposed to a stimulant; at least one upper three-dimensionalspace filling layer disposed on said core member, said upperthree-dimensional space filling layer comprised of an array of out ofplane truss units; at least one lower three-dimensional space fillinglayer disposed on said active core member opposite said upper spacefilling layer, said lower three-dimensional space filling layercomprised of an array of out of plane truss units; said at least some ofsaid upper and lower three-dimensional space filling layers are alignedrelative to one another such that they will interpenetrate whensubjected to the force.
 20. The multifunctional member of claim 19,wherein said out-of-plane truss units have a geometrical shape selectedfrom the group consisting of: tetrahedral, pyramidal, Kagome, cone,frustrum combinations thereof and other non-limiting arrangements. 21.The multifunctional member of claim 19, wherein said out-of-plane trussunits have hollow or solid leg members.
 22. The multifunctional memberof claim 19, wherein said out-of-plane truss form a perforated or solidsheet.
 23. A multifunctional member adapted for structural deformationand reformation, the multifunctional member comprising: at least oneactive core member, said active core member adapted to: deform intension if exposed to an external force, and reform from a deformedstate if exposed to a stimulant; at least one upper expandable layerdisposed on said core member, said upper expandable layer comprising anarray of expandable units, said upper expandable units having a basedimension as defined by the dimension substantially parallel to saidactive core member, and a height dimension as defined by the dimensionsubstantially perpendicular to said active core member; at least onelower expandable layer disposed on said active core member opposite saidupper space filling layer, said lower expandable layer comprised of anarray of expandable units, said lower expandable units having a basedimension as defined by the dimension substantially parallel to saidactive core member, and a height dimension as defined by the dimensionsubstantially perpendicular to said active core member, and said upperand lower expandable layers are adapted whereby when subject to theforce the height dimensions of at least some of the upper and lowerexpandable units decrease thereby deforming the active core member intension.
 24. The multifunctional member of claim 23, wherein said upperand lower expandable layers is a corrugated strip, corrugated band,corrugated ribbon, or corrugated sheet.
 25. The multifunctional memberof claim 23, wherein said deformed active core member is deformed in asubstantially lateral direction or lateral direction.
 26. Amultifunctional member adapted for structural deformation andreformation, the multifunctional member comprising: at least one activecore member, said active core member adapted to: deform in tension ifexposed to an external force, and reform from a deformed state ifexposed to a stimulant; at least one upper three-dimensional spacefilling layer disposed on said core member, said upper three-dimensionalspace filling layer comprised of an array of out of plane truss units,said upper truss units having a base dimension as defined by thedimension substantially parallel to said active core member, and aheight dimension as defined by the dimension substantially perpendicularto said active core member; at least one lower three-dimensional spacefilling layer disposed on said active core member opposite said upperspace filling layer, said lower three-dimensional space filling layercomprised of an array of out of plane truss units, said lower trussunits having a base dimension as defined by the dimension substantiallyparallel to said active core member, and a height dimension as definedby the dimension substantially perpendicular to said active core member,and said upper and lower three-dimensional space filling layers areadapted whereby when subject to the force the height dimensions of atleast some of the upper and lower truss units decrease thereby deformingthe active core member in tension.
 27. The multifunctional member ofclaim 26, wherein at least some of said upper and lower out of planetruss units are tetrahedral.
 28. The multifunctional member of claim 27,wherein at least one of said active core members is a hexagonal cellularsheet.
 29. The multifunctional member of claim 26, wherein at least someof said upper and lower out of plane truss units are pyramidal.
 30. Themultifunctional member of claim 29, wherein at least one of said activecore members is a square or rectangular cellular sheet.
 31. Themultifunctional member of claim 26, wherein said deformed active coremember is deformed in a substantially lateral direction or lateraldirection.
 32. A multifunctional member adapted for structuraldeformation and reformation, the multifunctional member comprising: atleast one active core member, said active core member adapted to: deformif exposed to an external force, and reform from a deformed state ifexposed to a stimulant; at least one upper exterior member disposed onsaid core member; and at least one lower exterior member disposed onsaid core member opposite said upper exterior member, wherein at least aportion of said at least one upper exterior member and at least aportion of said at least one lower member interpenetrate one anotherwhen subject to the force.
 33. A multifunctional member adapted forstructural deformation and reformation, the multifunctional membercomprising: at least one active core member, said active core memberadapted to: deform if exposed to an external force, and reform from adeformed state upon removal of the external force; at least one uppermember disposed on said core member, said upper member further comprisedof at least one protrusion, whereby said protrusions generallyprotruding in the direction of said active core member; at least onelower member disposed on said core member opposite said upper member,said lower member further comprised of at least one protrusion, wherebysaid protrusions generally protruding in the direction of said activecore member; and said at least some of said upper protrusions and lowerprotrusions are aligned relative to one another such they willinterpenetrate when subject to the force.
 34. The multifunctional memberof claim 33, wherein said active core is made from pseudo-elastic SMAmaterial or a superelastic SMA material.
 35. A multifunctional memberadapted for structural deformation and reformation, the multifunctionalmember comprising: at least one active core member, said active cellularcore member adapted to: deform if exposed to an external force, andreform from a deformed state upon removal of the external force; atleast one upper three-dimensional space filling layer disposed on saidcore member, said upper three-dimensional space filling layer comprisedof an array of out of plane truss units; at least one lowerthree-dimensional space filling layer disposed on said active coremember opposite said upper space filling layer, said lowerthree-dimensional space filling layer comprised of an array of out ofplane truss units; said at least some of said upper and lowerthree-dimensional space filling layers are aligned relative to oneanother such that they will interpenetrate when subjected to the force.36. A multifunctional member adapted for structural deformation andreformation, the multifunctional member comprising: at least one activecore member, said active core member adapted to: deform in tension ifexposed to an external force, and reform from a deformed state uponremoval of the external force; at least one upper expandable layerdisposed on said core member, said upper expandable layer comprising anarray of out of expandable units, said upper expandable units having abase dimension as defined by the dimension substantially parallel tosaid active core member, and a height dimension as defined by thedimension substantially perpendicular to said active core member; atleast one lower expandable layer disposed on said active core memberopposite said upper space filling layer, said lower expandable layercomprised of an array of expandable units, said lower expandable unitshaving a base dimension as defined by the dimension substantiallyparallel to said active core member, and a height dimension as definedby the dimension substantially perpendicular to said active core member,and said upper and lower expandable layers are adapted whereby whensubject to the force the height dimensions of at least some of the upperand lower expandable units decrease thereby deforming the active coremember in tension.
 37. A multifunctional member adapted for structuraldeformation and reformation, the multifunctional member comprising: atleast one active core member, said active core member adapted to: deformin tension if exposed to an external force, and reform from a deformedstate upon removal of the external force; at least one upperthree-dimensional space filling layer disposed on said core member, saidupper three-dimensional space filling layer comprised of an array of outof plane truss units, said upper truss units having a base dimension asdefined by the dimension substantially parallel to said active coremember, and a height dimension as defined by the dimension substantiallyperpendicular to said active core member; at least one lowerthree-dimensional space filling layer disposed on said active coremember opposite said upper space filling layer, said lowerthree-dimensional space filling layer comprised of an array of out ofplane truss units, said lower truss units having a base dimension asdefined by the dimension substantially parallel to said active coremember, and a height dimension as defined by the dimension substantiallyperpendicular to said active core member, and said upper and lowerthree-dimensional space filling layers are adapted whereby when subjectto the force the height dimensions of at least some of the upper andlower truss units decrease thereby deforming the active core member intension.
 38. A multifunctional member adapted for structural deformationand reformation, the multifunctional member comprising: at least oneactive core member, said active core member adapted to: deform ifexposed to an external force, and reform from a deformed state uponremoval of the external force; at least one upper exterior memberdisposed on said core member; and at least one lower exterior memberdisposed on said core member opposite said upper exterior member,wherein at least a portion of said at least one upper exterior memberand at least a portion of said at least one lower member interpenetrateone another when subject to the force.
 39. A multifunctional memberadapted for structural deformation and reformation, the multifunctionalmember comprising: at least one active core member, said active coremember adapted to: deform in tension if exposed to an external force,and reform from a deformed state if exposed to a stimulant; at least oneupper expandable layer disposed on said core member, said upperexpandable layer comprising an array of out of expandable units, saidupper expandable units having a base dimension as defined by thedimension substantially parallel to said active core member, and aheight dimension as defined by the dimension substantially perpendicularto said active core member; at least one lower expandable layer disposedon said active core member opposite said upper space filling layer, saidlower expandable layer comprised of an array of expandable units, saidlower expandable units having a base dimension as defined by thedimension substantially parallel to said active core member, and aheight dimension as defined by the dimension substantially perpendicularto said active core member, and said upper and lower expandable layersare adapted whereby when subject to the force the base dimensions of atleast some of the upper and lower expandable units increase therebydeforming the active core member in tension.
 40. The multifunctionalmember of claim 39, wherein said upper and lower expandable layers is acorrugated strip, corrugated band, corrugated ribbon, or corrugatedsheet.
 41. The multifunctional member of claim 39, wherein said deformedactive core member is deformed in a substantially lateral direction orlateral direction.
 42. A multifunctional member adapted for structuraldeformation and reformation, the multifunctional member comprising: atleast one active core member, said active core member adapted to: deformin tension if exposed to an external force, and reform from a deformedstate if exposed to a stimulant; at least one upper three-dimensionalspace filling layer disposed on said core member, said upperthree-dimensional space filling layer comprised of an array of out ofplane truss units, said upper truss units having a base dimension asdefined by the dimension substantially parallel to said active coremember, and a height dimension as defined by the dimension substantiallyperpendicular to said active core member; at least one lowerthree-dimensional space filling layer disposed on said active coremember opposite said upper space filling layer, said lowerthree-dimensional space filling layer comprised of an array of out ofplane truss units, said lower truss units having a base dimension asdefined by the dimension substantially parallel to said active coremember, and a height dimension as defined by the dimension substantiallyperpendicular to said active core member, and said upper and lowerthree-dimensional space filling layers are adapted whereby when subjectto the force the base dimensions of at least some of the upper and lowertruss units increase thereby deforming the active core member intension.
 43. The multifunctional member of claim 42, wherein at leastsome of said upper and lower out of plane truss units are tetrahedral.44. The multifunctional member of claim 43, wherein at least one of saidactive core members is a hexagonal cellular sheet.
 45. Themultifunctional member of claim 42, wherein at least some of said upperand lower out of plane truss units are pyramidal.
 46. Themultifunctional member of claim 45, wherein at least one of said activecore members is a square or rectangular cellular sheet.
 47. Themultifunctional member of claim 42, wherein said deformed active coremember is deformed in a substantially lateral direction or lateraldirection.
 48. A multifunctional member adapted for structuraldeformation and reformation, the multifunctional member comprising: atleast one active core member, said active core member adapted to: deformin tension if exposed to an external force, and reform from a deformedstate upon removal of the external force; at least one upper expandablelayer disposed on said core member, said upper expandable layercomprising an array of out of expandable units, said upper expandableunits having a base dimension as defined by the dimension substantiallyparallel to said active core member, and a height dimension as definedby the dimension substantially perpendicular to said active core member;at least one lower expandable layer disposed on said active core memberopposite said upper space filling layer, said lower expandable layercomprised of an array of expandable units, said lower expandable unitshaving a base dimension as defined by the dimension substantiallyparallel to said active core member, and a height dimension as definedby the dimension substantially perpendicular to said active core member,and said upper and lower expandable layers are adapted whereby whensubject to the force the base dimensions of at least some of the upperand lower expandable units increase thereby deforming the active coremember in tension.
 49. A multifunctional member adapted for structuraldeformation and reformation, the multifunctional member comprising: atleast one active core member, said active core member adapted to: deformin tension if exposed to an external force, and reform from a deformedstate upon removal of the external force; at least one upperthree-dimensional space filling layer disposed on said core member, saidupper three-dimensional space filling layer comprised of an array of outof plane truss units, said upper truss units having a base dimension asdefined by the dimension substantially parallel to said active coremember, and a height dimension as defined by the dimension substantiallyperpendicular to said active core member; at least one lowerthree-dimensional space filling layer disposed on said active coremember opposite said upper space filling layer, said lowerthree-dimensional space filling layer comprised of an array of out ofplane truss units, said lower truss units having a base dimension asdefined by the dimension substantially parallel to said active coremember, and a height dimension as defined by the dimension substantiallyperpendicular to said active core member, and said upper and lowerthree-dimensional space filling layers are adapted whereby when subjectto the force the base dimensions of at least some of the upper and lowertruss units increase thereby deforming the active core member intension.